This invention pertains to the formulation of rigid polyurethane and polyisocyanurate foam, and more particularly to a method that allows the formulator to predict physical properties of a formula prior to experimental determination. Rigid foam can be defined as a stable dispersion of gas in a solid rigid phase, said rigid phase being a polyurethane or polyisocyanurate polymer. It is common in art to refer to both polyurethane and polyisocyanurate foams as polyurethane foam. This convention will be maintained herein.
Polyurethane foams are products of significant commercial importance, being used in such useful commercial products ranging from building insulation, sound dampening materials, to gaskets, bedding and seat cushions. All of the products mentioned are a formulated material; that is they are created by the careful selection and blending of a plurality of individual components that are then mixed together using a specific manufacturing process to produce the final product. It is the task of the formulator to select the individual raw materials and proportion them with respect to each other into a final formula or recipe that with proper processing will produce the desired product. Formulation is often a repetitive process whereby the formulator prepares a written formula, then mixes it in the laboratory, tests a specimen made from the formula to determine its physical properties. The tests results are then compared to the design criteria. If the design criteria are not met, then the process is then repeated until the design criteria are met.
Formulation is a time consuming, expensive, and waste generating process. It consumes labor hours to design and test the formulas, raw materials to produce the test specimens, and the failed formulations generate waste that must be land filled. Thus a method that reduces the number of trial formulations to be produced and tested is a useful and desirable method. The invention described herein enables the formulator to reach the design criteria with less effort than the current art.
If the formulator could accurately predict the final physical properties of the written formula without having to complete an experimental trial for each formula, the number of experimental runs could be reduced. One of the preferred methods to reduce the number of experimental runs is to use statistical methods, often referred to as design of experiments or DOE. By entering a range of proportions of a series of raw materials, DOE is used to create a response surface map. The map describes a design space consisting of actual and theoretical physical properties of different formulas. Once the response surface map is created, theoretical formulas can be selected from the response surface map. The formulator then scans the response surface to find a theoretical formula the meets the design criteria. The formulator then prepares and tests the formula to confirm the predicted results.
Although DOE is effective, it is limited when compared to the method described herein. To use DOE the formulator must run multiple of experiments to create and map the design space. The method described herein, does not require the formulator to create a mapped design space. Rather it predicts final physical properties of each formula without requiring the formulator to prepare and test the formulation. In this way the invention is advantageous over the current art because the formulator does not have to prepare multiple formulas, instead he prepares only the formulas that match or closely approximate the design criteria.